Dental compositions

ABSTRACT

Dental compositions containing adjuvants are provided that have the capability of undergoing an increase in viscosity in response to an increase in temperature. In a preferred embodiment, the compositions also have the ability to reverse their viscosity in response to a decrease in temperature.

RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. Nos.09/190,541 now U.S. Pat. No. 6,312,666 and 09/190,717, now U.S. Pat. No.6,312,667 both filed Nov. 12, 1998, and both of which are incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to dental compositions having viscosities capableof responding to a change in temperature. The invention also relates tomethods of applying the composition directly onto a target area of thesubstrate.

BACKGROUND

In the dental art, the use of a dental coating composition is generallydesirable for a wide variety of applications, such as etching orbleaching. To attain proper application at the desired location, it isdesirable that the composition be controllable and slow to flow awayfrom the target site. Thus a high viscosity dental composition in theoral environment would be quite useful.

Currently available dental compositions are provided in seeminglyextreme viscosity states. That is, there exist compositions that havevery low viscosities as well as compositions that are highly thickenedand therefore possess high viscosity. Those with low viscosities aredifficult to control and have tendencies to flow away from the targetsite once they are applied. Compositions with high viscosities aredifficult to extrude through a small orifice.

Certain dental compositions may use thickeners such as fumed silica andpolyvinyl alcohols. Problems encountered in using these thickenersinclude aging, which results in non-homogenous gels which make handlingdifficult, and shear thinning, which reduces the viscosity of a gel whenextruded through an orifice and thinning at elevated temperatures.Thinning can result in a material that drips from the orifice and thatmay fail to remain localized at the desired point of application.

SUMMARY OF THE INVENTION

The present invention provides a dental composition suitable forapplication in the oral environment comprising a thermally responsiveviscosity modifier that is capable of undergoing an increase inviscosity in response to an increase in temperature. These compositionsalso preferably have the ability to reverse their viscosity upon thelowering of temperature.

Compositions of the invention work very well in the oral environmentwhere temperature is generally higher than ambient or the pre-treatmenttemperature of a composition. This differential in temperature thickensthe composition and thus provides a thickened, semi-solid or gel-likecomposition in the oral environment.

A preferred method of use of the invention comprises applying thecomposition directly onto the oral surface. Upon exposure of thecomposition to the oral temperature, the composition thickens to asemi-solid or gel-like state.

In one aspect, the present invention provides a method of applying adental composition in the oral environment using a dental compositioncomprising about 10% by weight to about 50% by weight of a thermallyresponsive viscosity modifier and an adjuvant, wherein the compositionis in a low viscosity state at a pre-treatment temperature and a highlyviscous state at a treatment temperature that is higher than thepre-treatment temperature. The method includes applying the compositionthrough an orifice, preferably the orifice of a syringe, onto a surface,wherein the composition is at the pretreatment temperature and in thelow viscosity state prior to being applied onto the surface, allowingthe composition to warm to the treatment temperature and increase inviscosity to the highly viscous state wherein the viscosity of thecomposition at the treatment temperature is at least about 10 times theviscosity of the composition at the pre-treatment temperature, andallowing the composition to remain on the surface. Preferably thepre-treatment temperature is at most about room temperature and thetreatment temperature is about body temperature. Preferred adjuvantsinclude acids, whitening agents, fluoride, anti-microbial agents, andmedicaments.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graphic illustration of the viscosity versus temperaturedata as described in Example 1.

FIG. 2 is a graphic illustration of the viscosity versus temperaturedata as described in Example 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a dental composition in a low viscositystate prior to application onto an oral surface, but which also ishighly viscous, thick and controllable at the target site. Thesecompositions are easily dispensed, applied, and manipulated when handledby the user, and are easily controlled upon application to the targetsite. Because the composition has a low viscosity initially at apre-treatment temperature, it requires lower syringe extrusion forces todeliver the compositions to the intended site. In turn, this would allowa user the alternative of using a brush or other applicator to apply thecomposition. In addition, production of low viscosity compositions mayprovide easier processing and greater uniformity and consistency.

Compositions of this invention are particularly suitable for use in theintraoral environment where a composition having a pre-treatmenttemperature at or lower than ambient (room temperature) is applied to auser's oral surface that is near or at oral temperature of about 30° C.to about 39° C. For certain dental applications, it is preferred thatthe composition be thermally reversible. In that application, thecomposition not only has the ability to increase its viscosity at anelevated intra-oral temperature, but also reverses or decreases itsviscosity upon a decrease in temperature.

The capacity of the dental composition to thicken at oral temperaturesis a critical feature of the invention, for it is in this property thatmany of the disadvantages of previous approaches are overcome. Thedissipative characteristic of liquid solutions is avoided since thecompositions herein experience thickening at the site of treatment.Moreover, the problems of formulation, handling, delivery andapplication of viscous compositions are overcome since the presentcompositions may be free-flowing liquids prior to treatment.

For example, the art of etching hard tissue typically requires etching atarget site or controlled areas of several teeth at one time. Currentetchant liquids are easy to dispense and apply, but these tend to flowaway from the target area of application. Consequently, an etch patchcould be larger than desired or, more undesirably, contact with the softtissue could occur, which can cause sensitivity or irritation. A largeetch patch unnecessarily increases the risk of decalcification duringtreatment. Some compositions have been provided in thickened states toprovide less flow and mobility; however, they are often difficult todispense.

Furthermore, other applications, such as dental whitening, suffer whenthe dental whitening compositions decrease in viscosity due to theincrease in temperature from the intraoral environment. This thinningand viscosity decrease creates a tendency for the whitening compositionto flow from the target location, resulting in a reduced amount ofwhitening composition available for treatment at the target location forthe desired length of time.

A “semi-solid,” as used herein, is a material whose physical state isbetween the solid and liquid state, in which pure or mixed solvent orsolution is entrained within a network, and can alternatively beconsidered a gel. By “pure or mixed solvent and/or solution,” as statedherein, it is recognized that a mixture of solvents may be absorbed bythe network. Additionally, the solvent may include salts or otheradditives so as to form a solution, which may also be absorbed orentrained within the network.

“Thickening” as used herein, is where a composition undergoes asubstantial increase in the viscosity of the composition. The degree ofthickening is dependent on the initial viscosity of the composition.

In a preferred embodiment of the invention, the initial viscosity of thecomposition may be low enough such that the composition is in a liquidstate. Subsequently, upon exposure to a temperature of about near or atoral temperature, the viscosity increases to result in a thickenedcomposition. A viscosity increase in the range of about 10- to about100-fold can be experienced when the initial viscosity is such that thecomposition is a liquid. Thus, for example, a composition in a liquidstate may have a viscosity of about 0 to about 7000 poise. In responseto an increase in temperature, the viscosity of the composition canincrease to at least about 10,000 poise. Upon the lowering of thetemperature, the composition preferably has the ability to reverse itsviscosity and return to flow properties of a liquid.

Yet another preferred embodiment of the invention is when the initialviscosity of the composition is at a level at which the composition isin a semi-solid state at pre-treatment temperature (viscosity is atleast about 5000 poise), and upon exposure to a higher treatmenttemperature, the composition transforms into an “ultra-thick”composition or one with a substantially higher viscosity and very lowflow characteristics. For compositions having initially highviscosities, the degree of thickening is typically about 2- to about5-fold.

The pre-treatment temperature is the temperature at which thecomposition is subjected to prior to application or treatment. The rangefor the pre-treatment temperature can be about 5° C. to about 29° C.,although there may be certain instances where the temperature may beoutside this range. Having a pre-treatment temperature at about 20° C.to about 25° C. allows the composition to be easily stored at ambient orroom temperature. Alternatively, the compositions of the invention canalso be advantageously stored at lower, refrigeration pre-treatmenttemperatures of about 5° C. to about 10° C. to provide improvedstability and shelf life.

The treatment temperature is the temperature at which the composition isexposed during intraoral application. This can be at or near bodytemperature, or about 30° C. to about 39° C.

In accordance with the invention, the dental composition consists of awater-miscible, physiologically compatible medium that is liquid atambient temperature below about 30° C. and experiences thickening atoral temperatures above about 30° C. It has been found that acomposition having a thickening transition temperature in the range offrom about 25° C. to about 40° C. is useful in the practice of thepresent invention. Preferably, the thickening occurs in a temperaturerange of from about 25° C. to about 39° C., and more preferably fromabout 30° C. to about 35° C.

Compositions of this invention are comprised of a solvent and one ormore polymeric substances that provide the desired viscosity increase atthe desired elevated temperature range in the said composition.Optionally, adjuvants may be added to the composition. Preferably, thecomposition of this invention should be physiologically compatible sothat no adverse reaction occurs if the dental composition comes incontact with human tissue or fluids.

As used herein, a “thermally responsive viscosity modifier” is one ormore polymeric substances that provide the composition or polymericsystem the capability of substantially changing its viscosity inresponse to a change in temperature. Suitable polymeric substancesuseful as thermally responsive viscosity modifiers includepolyoxyalkylene polymers, particularly the polymeric surfactantsavailable under the tradename PLURONIC. This class of polymers isavailable commercially from BASF Wyandotte Corporation. Otherpolyoxyalkylene polymers may also be useful as a thermally-responsivecomposition material.

A preferred dental composition in accordance with this inventioncomprises an aqueous solution of a selectedpolyoxyethylene-polyoxypropylene block copolymer. A compositioncomprising polyoxyethylene-polyoxypropylene block copolymers in whichthe number of polyoxyethylene units is at least about 50% of the numberof units in the total molecule, and the block copolymer having anaverage molecular weight of from about 1100 to about 15,500 has beenfound to be particularly useful. It is more preferable that acomposition comprises about 70% polyoxyethylene units of the totalnumber of monomeric units in the copolymer and the copolymer has anaverage molecular weight of about 11,500. PLURONIC F-127 is a materialthat meets these criteria.

The PLURONIC polymers are closely related block copolymers that may begenerically classified as polyoxypropylene-polyoxyethylene condensatesthat terminate in primary hydroxyl groups. These polymers are formed bythe condensation of propylene oxide into a propylene glycol nucleusfollowed by the condensation of ethylene oxide onto both ends of thepolyoxypropylene base. The polyoxyethylene hydrophilic groups on theends of the base pre-polymer are controlled in length to constitute fromabout 10% to about 80% by weight of the final polymer.

The PLURONIC polymer series of products may be represented empiricallyby the formula: HO(C₂H₄O)_(a)(C₃H₆O)_(b)(C₂H₄O)_(c)H where a and c arestatistically equal.

The concentration of the block copolymers is an important parameter andcan be formulated in such a manner corresponding to the othercomponents' concentrations. By adjusting the concentration of thecopolymer to accommodate other solutes present in the composition, anydesired liquid to semi-solid transition temperature in the criticalrange of above ambient temperature and below body temperature can beachieved. Thus, the principal consideration is the selection of aconcentration that, in conjunction with all of the constituents of thetotal composition, will provide a liquid to semi-solid transitiontemperature in the required range.

It has been found that a useful block copolymer concentration is fromabout 5% to about 40% by weight (wt. %) of the composition, particularlyfrom about 15 wt. % to about 26 wt. % of the composition. Excellentresults have been obtained using aqueous solutions having from about 17wt. % to about 29 wt. % of PLURON1C F-127. Increased polymerconcentrations may be required in highly acidic systems to affect thesame results as in a less acidic system so that, in optimizing thethickening or gelation characteristics for a system, the pH of thesolution must be taken into account.

Particularly preferred polymers for the present invention are thePLURONIC F-127 and F-108. These viscosity modifiers are block copolymersof ethylene oxide and propylene oxide. Thickening tendencies of blockcopolymers increase as ethylene oxide content and total molecular weightincrease. Thermally responsive block copolymers have been disclosed inU.S. Pat. Nos. 4,474,751; 4,474,752; 5,441,732; and 5,252,318, as wellas the Product Catalog, “BASF Performance Chemicals,” all the teachingsof which are incorporated by reference herein. These block copolymersoffer extremely low toxicity and a high degree of mildness forapplications involving human contact.

A preferred solvent for the composition of this invention is water. Theconcentration of water in the composition can be in the range of fromabout 30 wt. % to about 90 wt. % of the composition. Preferably, watercan exist in the range of about 40 wt. % to about 80 wt. % of thecomposition. The water used in forming the aqueous solution ispreferably purified, as by distillation, filtration, ion-exchange, orthe like.

Co-solvents may be used, including anhydrous solutions comprising apolyol component such as propylene glycol or polyethylene glycol.Glycerin may also be used as a constituent of the composition.

Adjuvants can be added to the composition for various purposes (e.g.,acids for dental etchants and whitening agents for dental whiteners).For example, a preferred embodiment of the invention can containfluoride, a desirable additive in the oral composition. Additives mayalso be included in the composition to promote the stability of theformulation. Anti-microbial agents, anti-fungal agents, andpreservatives may be added to the composition to improve shelf-life. Thecompositions may further include other adjuvants such as medicaments,indicators, dyes, wetting agents, buffering agents, thixotropes, polyolsand the like, contingent upon attainment of the desired degree ofetching performance and suitability for use on the desired hard tissue.For example, a composition may contain indicators that communicate tothe user the degree of etching that has been performed on the hardtissue. The compositions may further include other adjuvants such asfillers, cariostatic agents and flavorings.

When the dental composition is a dental etchant, acids may be added tothe composition as an adjuvant. Acids for use in the present inventioncan be inorganic or organic acids, and if organic can be monomeric,oligomeric or polymeric. If desired, a precursor to the acid such as anacid anhydride, e.g., 4-Methacryloxyethyl Trimellitate Anhydride(4-META), acid halide (including inorganic acid halides such as Lewisacids, e.g., ferric chloride, and organic acid halides), or ester can beused in place of the acid itself, e.g., to generate the desired acid insitu. Suitable acids include mineral acids, carboxylic acids, sulfonicacids, and phenols, with carboxylic acids, alkylsulfonic acids,arylsulfonic acids, and phosphonic acids being preferred.

The acid has a pKa in water that is less than or equal to that ofphenol. Preferably, the pKa of the acid is between about −20 and about+10, more preferably between about −10 and about +5.

The acid can be liquid or a solid; if a solid it should be dissolved ina suitable solvent to enable the acid to wet the hard tissue. Liquidacids can also be dissolved in a suitable solvent, e.g., in order tofacilitate wetting. Preferred solvents for the acid are the film formercosolvents discussed in more detail below.

Suitable inorganic acids include hydrobromic acid, hydrochloric acid,nitric acid, phosphoric acid, and sulfuric acid. Suitable organic acidsinclude acetic acid, α-chloropropionic acid,2-acrylamido-2-methylpropane sulfonic acid, acrylic acid,benzenesulfonic acid, benzoic acid, bromoacetic acid,10-camphorquinone-sulfonic acid, 10-camphorsulfonic acid, chloroaceticacid, citraconic acid, citric acid, dibromoacetic acid, dichloroaceticacid, di-Hema ester of 1,2,4,5 benzenetetracarboxylic acid,2,4-dinitrophenol, ethylenediaminetetraacetic acid (EDTA), the mono-,di- and trivalent salts of EDTA, formic acid, fumaric acid,2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, maleic acid,methacrylic acid, 2-naphthalene sulfonic acid, oxalic acid,p-nitrophenol, phenol, phosphorous acid esters (such as2,2′-bis(a-methacryloxy-b-hydroxypropoxyphenyl) propane diphosphonate(Bis-GMA diphosphonate), dibutyl phosphite, di-2-ethyl-hexyl phosphate,di-2-ethyl-hexyl phosphite, hydroxyethyl methacrylate monophosphate,glyceryl dimethacrylate phosphate, glyceryl-2-phosphate,glycerylphosphoric acid, methacryloxyethyl phosphate, pentaerythritoltriacrylate monophosphate, pentaerythritol trimethacrylatemonophosphate, dipentaerythritol pentaacrylate monophosphate, anddipentaerythritol pentamethacrylate monophosphate), pivalic acid,propionic acid, toluene sulfonic acid, tribromoacetic acid,trichloroacetic acid, trifluoroacetic acid, trifluoromethanesulfonicacid, and trihydroxybenzoic acid. Mixtures of such acids can be used ifdesired.

In the practice of the present invention, the hard tissues that can beetched include human and animal tissues such as teeth, including thecomponent parts which are enamel, dentin, and cementum. The inventionhas particular utility for etching dentin, sclerotic dentin, enamel, andcervical enamel. In a preferred method of the invention, the etchant ispermitted to stand on the hard tissue for a desired period of time,readily volatile cosolvents are removed therefrom (e.g., by air-drying)to modify the surface of the hard tissue. Delivery of the etchingcomposition of the invention may be performed in various methods. Onemethod of delivery of the etching composition is the direct applicationof the composition onto the hard tissue. This may be done directly fromthe composition's container or dispenser such as a bottle, vial,syringe, or tube. Alternatively, it can be applied by using a brush topaint or coat the composition onto the hard tissue. The composition iskept on the hard tissue for a desired period to effectuate etching. Thelength of time the composition is in contact with the hard tissue woulddepend on the amount of etching desired.

A preferred method of use comprises first etching with the compositionof the present invention, followed by an application of a dentalmaterial on the tissue such as a sealant or coating, restorativematerial, adhesive, cement, dental primer or film former. Yet anotherpreferred method is first etching with the composition of the presentinvention, then followed by an application of a bonding agent forpurposes of bonding an orthodontic appliance onto a tooth. The inventionenables etching of hard tissue in order to improve the bond strength ordurability of a restorative or coating applied thereto.

Hard tissue to which the etchant is applied preferably is first cleanedusing conventional methods (e.g., by abrading it with a bur), rinsed(e.g., using water) and dried (e.g., using air). If desired, deepexcavations in teeth can be lined with a conventional basing material,(e.g., calcium hydroxide or a glass ionomer cement).

The acid should be allowed to stand on the surface of the hard tissuelong enough to provide the desired degree of etching. The standing timewill depend upon the particular acid employed, the type of hard tissueand its intended use, and the time available for carrying out theetching procedure. For etching dentin and enamel, standing times lessthan about 5 minutes, and preferably about 5 seconds to one minuteprovide very effective etching, although shorter or longer times can beused if desired.

When the dental composition is a dental whitener, whitening agents maybe added to the composition as an adjuvant. The whitening agent used inthe present invention may be any material that has the effect ofwhitening teeth. Whitening agents are preferably selected from hydrogenperoxide and its urea complex: carbamide peroxide (CO (NH₂)₂H₂O₂). Thesewhitening agents are also known by alternative names, including ureahydrogen peroxide, hydrogen peroxide carbamide, or perhydrol-urea.Alternatively, sodium hypochlorite may be suitable for use as thewhitening agent. The concentration of a whitening agent in thecomposition can vary depending upon its reactivity. With carbamideperoxide, for example, the currently preferred concentration range isfrom about 3% to about 40%, with a range from about 4% to about 21%being most preferred. In the case of hydrogen peroxide, which is morereactive than carbamide peroxide, the currently preferred concentrationrange is from about 2% to about 10%.

Various methods can be employed in using the whitening composition ofthis invention. One method of use of these whitening compositionsentails application of the composition to the tooth structure directlyfrom the composition's container or dispenser such as a bottle, syringe,or tube. Alternatively, the whitening composition can be applied byusing a brush to paint it onto the tooth surface. The composition iskept on the user's tooth surface(s) for a desired time period toeffectuate whitening. The length of time the composition is in contactwith the tooth surface(s) would depend on the amount of discolorationthe user prefers to remove.

In a preferred method, the whitening composition is loaded into a dentaltray. Such dental trays can be custom fitted to a user's dentition andbe made with or without reservoirs. A preferred reservoir is describedin U.S. Pat. No. 6,126,443. Dental trays can be made from varyingthicknesses and softness of pliable thermo-formable plastic materials.Typically, these materials are 0.02-0.08 inches thick. After dispensingor loading the whitening composition into the dental tray, the user thenplaces the loaded tray into the mouth and initiates thickening of thecomposition. The thickening occurs when the composition is exposed tothe elevated treatment temperature of the oral environment. The tray isretained in the mouth to effectuate whitening of the tooth surface(s)for a sufficient period of time to remove discoloration.

An alternative method of use incorporates a pre-warmed dental tray intowhich the whitening composition is loaded. Upon contact of thecomposition having a pre-treatment temperature, with the tray having ahigher temperature, the composition experiences thickening. This methodprovides easy handling of a loaded tray into a user's mouth, withminimal fear of the composition moving to an undesired section of thetray or having the composition flow out of the tray. Where the dentalcompositions are thermally reversible, the composition can be readilyremoved from the hard tissue by cooling the material below the liquid tosemi-solid transition temperature, thus reversing the thickening effect.This can be accomplished with cool water or other physiologicallycompatible liquid. Alternatively, the concentrations of the componentsin the composition may be adjusted and diluted by adding water or otherliquid solution. By adjusting the concentrations of the components, thetransition temperature is correspondingly adjusted, and thus providesthe user the ability to remove the composition even with warm solutions.Water or other liquid solutions may be administered through a rinsingcup, squirt bottle, a liquid dispensing dental tool, or any other liquiddispensing device that can provide solution to the oral environment.Preferably, administering cool or cold water provides a significantdecrease in viscosity. Alternatively, the composition may be brushed,wiped, or blown off.

These and other aspects of the invention are illustrated by thefollowing examples that should not be viewed as limiting in scope.Unless otherwise indicated, all molecular weights are number averagemolecular weights and all ratios, parts and percentages are by weight.

EXAMPLES Example 1

Etching compositions were made in which the acid used was 3M EtchantLiquid manufactured by 3M Dental Products Division. Sample compositions2 through 7 were mixed such that the compositions contained 15-30% byweight of PLURONIC F127 (BASF) in 3M Etchant Liquid (3M Co., St. Paul,Minn.).

Complex viscosity versus temperature data were obtained using acontrolled strain rheometer (“RDA2”, Rheometrics Scientific, Piscataway,N.J.). A parallel plate geometry was used with a plate diameter of 25 mmand a gap of approximately 1 mm. Samples were subjected to anoscillatory strain of 10% applied at a frequency of 1 rad/sec while thetemperature was ramped from 15° to 45° C. (3° C./min). The resultingdata is shown in FIG. 1.

The compositions 1-7 are phosphoric acid gels of the following types:

-   Composition #-   Comparative 1 3M Dental Etchant Gel containing fumed silica (3M Co.)-   Comparative 2 Contains 15.3% PLURONIC F127+84.7% 3M Etchant Liquid-   Comparative 3 Contains 18.4% PLURONIC F127+81.6% 3M Etchant Liquid-   Comparative 4 Contains 21.3% PLURONIC F127+78.7% 3M Etchant Liquid-   Comparative 5 Contains 24.0% PLURONIC F127+76% 3M Etchant Liquid-   Comparative 6 Contains 26.5% PLURONIC F127+73.5% 3M Etchant Liquid-   Comparative 7 Contains 28.8% PLURONIC F127+71.2% 3M Etchant Liquid    FIG. 1 illustrates the viscosity of each composition in response to    temperature. As seen in the Figure, the liquid to gel transition    temperature for the compositions containing PLURONIC, as shown by    the substantial increase in viscosity in response to temperature    increases, is dependent on the concentration of the PLURONIC block    copolymer. The silica filled etchant (Comparative Composition 1)    maintained a high, consistent viscosity throughout the temperature    range.

Example 2

Compositions 2 and 7 were further tested using a laboratory convectionoven, heated to a temperature of approximately 45° C.

The concentration of PLURON1C F127 had significant impact on the initialviscosity of the acid etchant gel as well as the temperature at whichthe acid formed an “immobile gel.” An “immobile gel” indicates that thegel did not flow readily under its own weight in small volumes but wasstill able to be easily manipulated into new positions using hand-helddental instruments. The composition that contained 15.3% PLURONIC F127had a low initial viscosity similar to that of 3M Etchant Liquid and didnot form an immobile gel at approximately body temperature but did forman immobile gel at approximately 45° C. The composition containing 28.8%PLURONIC F127 was a thick liquid when cooled in a refrigerator atapproximately 5° C., but was an immobile gel at room temperature ofapproximately 24° C.

Example 3

An acid composition (gel) containing 24% PLURONIC F127 and 76% 3MEtchant Liquid was placed on a bovine tooth heated to 37° C. The gel wasextruded from a syringe as a liquid but formed an immobile gel oncontact with the tooth. The gel was left in place for 30 seconds, washedwith cold water and dried in the air. There was an obvious differencebetween the etched and unetched surfaces indicating that the acid gelwas effective.

Example 4

An acid gel containing 19.4% PLURONIC F127, 8.1% citric acid (Aldrich,Milwaukee, Wis.) and 72.5% DI water was placed on a bovine tooth heatedto 37° C. The gel was extruded from a bottle as a liquid but formed animmobile gel on contact with the tooth. The gel was left in place for 45seconds, washed with cold water and air dried. There was an obviousdifference between the etched and unetched surfaces indicating that theacid gel was effective.

The citric acid and phosphoric acid gels had similar initial viscosityand gel characteristics with significantly different levels of PLURONICF127. More PLURONIC F127 is required in highly acidic systems to affectthe same results as in a less acidic system so that, in optimizing thegelation characteristics for a system, pH of the stock etchant solutionmust be taken into account.

Preparation of Stock Solution 1

An aqueous stock solution containing approximately 15% hydrogen peroxide(H₂O₂) was prepared by transferring 5 grams of a 30% H₂O₂ (J. T. Baker)and 5 grams of distilled water to a glass vial. The stock solution wasmixed thoroughly.

Preparation of Stock Solution 2

An aqueous stock solution containing approximately 20% urea hydrogenperoxide (carbamide peroxide) was prepared by transferring 4 grams of97% urea hydrogen peroxide (Sigma) and 16 grams of distilled water to aglass vial. The stock solution was mixed thoroughly. (The hydrogenperoxide content of the urea hydrogen peroxide was about 35%). Stocksolution contained about 7% H₂O₂.

Example 5

A thermally-reversible hydrogen peroxide composition was prepared bytransferring the ingredients below to a glass vial and mixing thoroughlyuntil a colorless and transparent liquid solution was obtained.

Stock Solution 1 1.60 grams PLURONIC F127 (BASF) 0.40 grams 2.00 gramsThe above solution contained approximately 12% hydrogen peroxide, 68%water and 20% PLURONIC F127. The glass vial containing the liquidperoxide solution was warmed to body temperature by holding the vial ina human hand. Following about one to two minutes, the liquid wastransformed into a colorless, transparent composition that did not flowupon inverting the vial. The vial was allowed to cool to roomtemperature wherein the composition was transformed back to the lowviscosity state. This cycle was repeated several limes with the sameoutcome.

The liquid and semi-solid (gel) states were both semi-quantitativelyevaluated for hydrogen peroxide utilizing hydrogen peroxide analysisstrips. The analysis utilized “EM Quant Peroxide Test Strips” (EMScience Gibbstown, N.J., Catalog No. 10011-1). The compositions wereevaluated according to the manufacturer's directions.

Results of the tests indicated that both the liquid and semi-solidstates contained significant amounts of available peroxide.

The same sample was re-evaluated 2 months later and found to stillexhibit thermally-reversible characteristics and comparable hydrogenperoxide levels based on the semi-quantitative analysis.

Example 6

A thermally reversible composition containing urea hydrogen peroxide wasprepared by transferring the ingredients below to a glass vial andmixing thoroughly until a colorless and transparent liquid solution wasobtained.

Stock Solution 2 4.00 grams PLURONIC F127 (BASF) 1.00 grams 5.00 gramsThe above solution contained approximately 16% urea hydrogen peroxide(or about 5.6% hydrogen peroxide), 64% water and 20% PLURONIC F127. Theglass vial containing the liquid peroxide solution was warmed to bodytemperature by holding the vial in a human hand. After about 1 minute,the liquid transformed to a colorless, transparent composition that didnot flow upon inverting the vial. The vial was allowed to cool to roomtemperature wherein the semi-solid composition was transformed back tothe low viscosity state. This cycle was repeated several times with thesame outcome.

The liquid and semi-solid states were both semi-quantitatively evaluatedfor hydrogen peroxide utilizing hydrogen peroxide analysis strips, EMQuant Peroxide Test Strips (EM Science; Gibbstown, N.J., Catalog No.10011-1), according to the manufacturer's directions. Both the liquidand semi-solid states indicated the presence of significant amounts ofavailable peroxide.

The same sample was re-evaluated 9 days later and found to still exhibitthermally-reversible characteristics and comparable hydrogen peroxidelevels based on the semi-quantitative analysis.

Table 1 summarizes the results of the two previous examples. The “+”indicates an increase in the viscosity. The indicates a decrease in theviscosity. The presence of hydrogen peroxide as indicated in the tableare the results obtained from the semi-quantitative test using the EMQuant Peroxide Test Strips and test method.

TABLE 1 H₂O₂ 35° C. 25° C. Present % 35° C. viscosity 25° C. viscosityH₂O₂ @ 9 Peroxide viscosity @ 9 days viscosity @ 9 days Present daysExample 5 12 + + − − Yes Yes Example 6 16 + + − − Yes Yes

Example 7

Several compositions have been evaluated for viscosity as a function oftemperature. The compositions are described below:

TABLE 2 Comparative Sample A Physical Physical parts by % by AppearanceAppearance Component weight (g) weight at 23° C. at body temp Urea 20 20Low viscosity, Low viscosity, hydrogen colorless liquid Colorless liquidperoxide Water 80 80

TABLE 3 Sample B Physical Physical Parts by % by Appearance atAppearance at Component weight (g) weight 23° C. Body temp Urea 20 16Low viscosity, non-flowing, hydrogen Colorless liquid colorless gelperoxide Water 80 64 PLURONIC 25 20 F-127

TABLE 4 Sample C Physical Physical Parts by % by Appearance atAppearance at Component weight (g) weight 23° C. Body temp Urea 1.6 14.7Non-flowing, Non-flowing, hydrogen colorless gel colorless gel peroxideWater 6.4 58.7 PLURONIC 2.0 18.3 F-127 CAB-O-SIL 0.9 8.3 M-5* (fumedsilica) *available from Cabot Corp. (Boston, MA)

Samples were further evaluated for viscosity as a function oftemperature between 15° C. and 45° C. utilizing a Rheometrics RDA IIRheometer. Complex viscosity, η* (units of measure is in Poise), versustemperature data were obtained using a controlled strain rheometer(“RDA2”, Rheometrics Scientific, Piscataway, N.J.). A parallel plategeometry was used with a plate diameter of 25 mm and a gap ofapproximately 1 mm. Samples were subjected to an oscillatory strain of10% applied at a frequency of 1 rad/sec while the temperature was rampedfrom 15° C. and 45° C. (3° C./min).

Set out below is the RDA viscosity data. FIG. 2 illustrates that aqueouscompositions containing PLURONIC F127 polymer exhibit a relatively sharpincrease in viscosity upon warming from room temperature to about 45° C.Sample C, which exhibited semi-solid-like characteristics at roomtemperature (due to the incorporation of a fumed silica), also increasedsubstantially upon an increase in temperature.

TABLE 5 A B C Temp η° Temp η° Temp η° ° C. P ° C. P ° C. P 14.02 9.7542417.88 2308.56 18.5 52951.1 14.28 3.35258 17.88 2379.72 18.3 42757.915.36 7.33292 18.54 2587.46 18.79 41559.9 17.28 3.46242 19.42 3111.4119.64 41144.7 19.46 5.85152 20.91 3711.59 20.76 41347.4 21.12 5.7995322.36 4580.71 22.09 42047 22.89 7.09599 23.72 5661.42 23.51 43615.724.91 4.19887 25.46 7221.65 24.04 45494.3 26.31 0.87001 26.85 8940.3826.03 48768.7 28.23 3.13629 28.73 25375.6 27.94 55250.6 30.12 4.5741130.7 29698.2 29.57 82062.6 31.6 4.7215 32.07 33651.8 31.31 94988.5 33.29.01765 33.57 37181.2 32.83 1.04E + 05 35.02 8.0025 35.22 40557.8 34.361.09E + 05 36.75 2.94618 36.89 43766.3 36.09 1.13E + 05 38.44 4.2462638.43 46677.4 37.49 1.20E + 05 40.85 1.08273 40.01 49322.7 38.95 1.26E +05 42.92 5.04081 41.84 52296.6 40.7 1.32E + 05 43.52 54490.4 42.21.36E + 05 43.9 1.39E + 05

1. A method of applying a dental composition in the oral environment toa tooth structure using an aqueous dental composition comprising about10% by weight to about 50% by weight of a thermally responsive viscositymodifier one or more polymers, water, and an one or more adjuvants,wherein the composition is in one or more polymers is a polyoxyalkylenepolymer, which provides the composition with a lower viscosity state ata pre-treatment temperature and a highly viscous higher viscosity stateat a treatment temperature that is higher than the pre-treatmenttemperature, comprising: applying the composition through an orificeonto a surface of the tooth structure, wherein the composition is at thepretreatment temperature and in the lower viscosity state prior to beingapplied onto the surface of the tooth structure, allowing thecomposition to warm to the treatment temperature and increase inviscosity to the highly viscous higher viscosity state wherein theviscosity of the composition at the treatment temperature is at leastabout 10 times the viscosity of the composition at the pre-treatmenttemperature, and allowing the composition to remain on the surface ofthe tooth structure.
 2. The method of claim 1 wherein the pre-treatmenttemperature is at most about room temperature.
 3. The method of claim 1wherein the treatment temperature is about body temperature.
 4. Themethod of claim 1 wherein the thermally responsive viscosity modifier isa polyoxyalkylene polymer.
 5. The method of claim 1 wherein thecomposition further comprises a solvent.
 6. The method of claim 1wherein the viscosity of the composition at the treatment temperature isabout 10 times to about 100 times the viscosity of the composition atthe pre-treatment temperature.
 7. The method of claim 1 wherein thecomposition decreases in viscosity upon cooling from the treatmenttemperature.
 8. The method of claim 7 further comprising removing thecomposition from the surface by cooling the composition from thetreatment temperature.
 9. The method of claim 8 wherein the compositionis cooled by application of a cool liquid.
 10. The method of claim 9wherein the liquid comprises water.
 11. The method of claim 1 whereinapplying the composition onto a surface comprises applying thecomposition onto hard tissue.
 12. The method of claim 1 wherein applyingthe composition through an orifice comprises applying the compositionthrough an orifice of a syringe.
 13. The method of claim 1, wherein thedental composition comprises about 17% by weight to about 40% by weightof a thermally responsive viscosity modifier the one or more polymers.14. The method of claim 1, wherein the adjuvant is selected from thegroup consisting of acids and medicaments.
 15. The method of claim 1,wherein the adjuvant is selected from the group consisting of whiteningagents and medicaments.
 16. A method of applying a dental composition inthe oral environment to a tooth structure using an aqueous dentalcomposition comprising about 10% by weight to about 50% by weight of athermally responsive viscosity modifier one or more polymers, water, andan one or more adjuvants selected from the group consisting of fluoride,anti-microbial agents, anti-fungal agents, and cariostatic agents,wherein the composition is in one or more polymers is a polyoxyalkylenepolymer, which provides the composition with a lower viscosity state ata pre-treatment temperature and a highly viscous higher viscosity stateat a treatment temperature that is higher than the pre-treatmenttemperature, comprising: applying the composition through an orificeonto a surface of the tooth structure, wherein the composition is at thepretreatment temperature and in the lower viscosity state prior to beingapplied onto the surface of the tooth structure, allowing thecomposition to warm to the treatment temperature and increase inviscosity to the highly viscous higher viscosity state wherein theviscosity of the composition at the treatment temperature is at leastabout 10 times the viscosity of the composition at the pre-treatmenttemperature, and allowing the composition to remain on the surface ofthe tooth structure.
 17. The method of claim 1, wherein the aqueouscomposition includes a salt.
 18. A method of applying a dentalcomposition to a tooth structure using an aqueous dental compositioncomprising about 10% by weight to about 50 % by weight of one or morepolymers, water, and one or more adjuvants, wherein the one or morepolymers is a polyoxyalkylene polymer, which provides the compositionwith a lower viscosity state at a pre-treatment temperature and a higherviscosity state at a treatment temperature that is higher than thepre-treatment temperature, comprising: applying the composition throughan orifice onto a surface of the tooth structure, wherein thecomposition is at the pretreatment temperature and in the lowerviscosity state prior to being applied to the surface of the toothstructure, allowing the composition to warm to the treatment temperatureand increase in viscosity to the higher viscosity state wherein theviscosity of the composition at the treatment temperature is at leastabout 2 times the viscosity of the composition at the pre-treatmenttemperature, and allowing the composition to remain on the surface ofthe tooth structure.
 19. A method of applying a dental composition to atooth structure using an aqueous dental composition comprising about 10%by weight to about 50 % by weight of one or more polymers, water, andone or more adjuvants, wherein the one or more polymers is apolyoxyalkylene polymer, which provides the composition with a viscosityof about 0 to about 7000 poise at a pre-treatment temperature and aviscosity of at least about 10,000 poise at a treatment temperature thatis higher than the pre-treatment temperature, comprising: applying thecomposition through an orifice onto a surface of the tooth structure,wherein the composition is at the pretreatment temperature and has aviscosity of about 0 to about 7000 poise prior to being applied to thesurface of the tooth structure, allowing the composition to warm to thetreatment temperature and increase in viscosity to at least about 10,000poise, and allowing the composition to remain on the surface of thetooth structure.
 20. A method of applying a dental composition to atooth structure using an aqueous dental composition comprising about 10%by weight to about 50 % by weight of one or more polymers, water, andone or more adjuvants, wherein the one or more polymers is apolyoxyalkylene polymer, which provides the composition with a liquidand lower viscosity state at a pre-treatment temperature and a higherviscosity state at a treatment temperature that is higher than thepre-treatment temperature, comprising: applying the composition throughan orifice onto a surface of the tooth structure, wherein thecomposition is at the pretreatment temperature and in the liquid andlower viscosity state prior to being applied to the surface of the toothstructure, allowing the composition to warm to the treatment temperatureand increase in viscosity to the higher viscosity state such that thecomposition forms an immobile gel, and allowing the composition toremain on the surface of the tooth structure.
 21. The method of claims18, 19, or 20 wherein the pre-treatment temperature is at most aboutroom temperature.
 22. The method of claims 18, 19, or 20 wherein thetreatment temperature is about body temperature.
 23. The method ofclaims 18, 19, or 20 wherein the composition further comprises asolvent.
 24. The method of claims 18, 19, or 20 wherein the viscosity ofthe composition at the treatment temperature is about 10 times to about100 times the viscosity of the composition at the pre-treatmenttemperature.
 25. The method of claims 18, 19, or 20 wherein theviscosity of the composition at the treatment temperature is about 2times to about 5 times the viscosity of the composition at thepre-treatment temperature.
 26. The method of claims 18, 19, or 20wherein the composition decreases in viscosity upon cooling thecomposition from the treatment temperature.
 27. The method of claim 26further comprising removing the composition from the surface by coolingthe composition from the treatment temperature.
 28. The method of claim27 wherein the composition is cooled by application of a cool liquid.29. The method of claim 28 wherein the liquid comprises water.
 30. Themethod of claims 18, 19, or 20 wherein applying the composition throughan orifice comprises applying the composition through an orifice of asyringe.
 31. The method of claims 18, 19, or 20, wherein the dentalcomposition comprises about 17% by weight to about 40% by weight of theone or more polymers.
 32. The method of claims 18, 19, or 20, whereinthe adjuvant is selected from acids and medicaments.
 33. The method ofclaims 18, 19, or 20 wherein the adjuvant is selected from whiteningagents and medicaments.
 34. The method of claims 18, 19, or 20 whereinthe adjuvant is selected from fluoride, anti-microbial agents,anti-fungal agents, and cariostatic agents.
 35. The method of claims 18,19, or 20, wherein the aqueous composition includes a salt.
 36. Themethod of claims 18, 19, or 20 wherein the viscosity of the compositionat the pre-treatment temperature is at least about 5000 poise.
 37. Themethod of claims 18 or 20 wherein the viscosity of the composition atthe treatment temperature is at least about 10,000 poise.